At least one person was killed in a building collapse in Mexicali, Mexico, according to the assistant director of civil protection in Tijuana. The other victim died when he ran from his residence into the street and was hit by a car, said Alfredo Escobedo, Mexico's director of civil protection.

All 100 injuries are concentrated in Mexicali, Escobedo said.

In California and Arizona, there were no immediate reports of injuries and only limited reports of damages.

The quake struck at 3:40 p.m. (6:40 p.m. ET) about 110 miles east-southeast of Tijuana, Mexico, according to the U.S. Geological Survey.

Pictures from Mexicali, a major metropolitan area and the capital of Mexico's Baja California state, showed sides ripped off buildings, telephone poles toppled, roads cracked and supermarket aisles strewn with food that had fallen off shelves.

The entire city has lost power, according to Alan Sandoval, Tijuana's assistant director of civil protection.

"We have not felt a shake like that since about 1979," Michelle Tapia told CNN from Brawley, California.

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Joe Madison was shopping at a Wal-Mart in Palm Springs, California, when he felt the earthquake.

"I felt the entire store move, and people went running for the exits," he said.

Madison said people gathered outside in the parking lot until the shaking stopped.

"We felt it for about 30 seconds. It was rolling," San Diego County sheriff's Lt. Scott Ybarrondo told CNN. "Nothing fell off the walls here, but we have reports of pictures falling off walls elsewhere in the county."

The quake was the largest in the Baja California area since 1992, the USGS reported.

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The 1992 quake, which struck in Landers, California, triggered an earthquake the next day in Nevada and another quake 11 days later in Southern California, according to USGS seismologist Lucy Jones. Both were 5.7 magnitude quakes.

Jones said Sunday's quake also could trigger others in the coming days, though she said the relatively quiet hours after Sunday's quake make other big quakes less likely.

There have been three large aftershocks so far, including one that registered a 5.5 magnitude, and other smaller temblors, USGS said.

Chandeliers swung and water sloshed around in swimming pools in the Los Angeles suburbs, witnesses reported, while posters to Twitter reported feeling the quake in Phoenix, Arizona.

Capt. Steve Ruda, a spokesman for the Los Angeles city fire department, said there were isolated power outages and a few people reported trapped in elevators, but no injuries or structural damage were reported.

Nine minutes after the Mexico quake, a magnitude 4.1 quake rattled windows in Santa Rosa, north of San Francisco. No damage was reported there, and Susan Potter, a USGS geophysicist, told CNN that was a separate quake from the one that struck in the Baja California desert.

The USGS initially reported that the Baja California quake had a 6.9 magnitude. The USGS upgraded the quake about an hour later.